Various thermal engines are known in the art. Some use shape memorizing alloys, some use thermo-chemical fluids, and some use the expansion of high purity paraffin.
Current devices powered by the melting of paraffin are based on the concept of a paraffin actuator. These devices are referred to as linear paraffin engines. These devices involve a high purity paraffin-filled space enclosed in a cylinder into which an actuator rod is placed. If the paraffin is melted, then its corresponding high volume expansion factor of 15% forces the actuator rod to emerge from the cylinder. Actuation can be active or passive. In the former case, the paraffin is melted by heating filaments. Passive actuation, on the other hand, is triggered by an environmental temperature increase. The desired response temperature is selected via the use of the proper type of paraffin.
Benefits for aerospace applications include the following:
high reliability due to utmost mechanical simplicity PA1 light weight (typically 2 ounces) PA1 low power consumption (typically 10 W) PA1 high output force (50-1000 lbf) PA1 operable with AC or DC Power PA1 high kick-off force PA1 gentle, smooth stroke PA1 resetability PA1 high cycle life PA1 precision PA1 long stroke capability PA1 wide range of actuation temperatures according to type of paraffin used PA1 option for magnetic cleanliness PA1 a temperature and motion control logic external to the engine mechanism. PA1 a section that is a mechanically self contained removable entity. PA1 include a circular disk (the rotor disk) into the rotor, or the circumference of which the actuator bars are mounted. PA1 provide a slit on the sides of the squeeze tube and boots facing the engine axis for the rotor disk to pass. PA1 aid section cooling in a ribs or the outside of the stator.
A shortcoming of the paraffin actuator is its limited stroke, which can be extended only at the cost of the actuator size. Consequently, linear actuators find their best applications in release mechanisms and latches. Their use to power a wide range of rotary or linear motion would entail a loss of power due to the complexity of gears involved. Certain operations, however, require a steady, strong force sustained over a considerable extent of motion. An example is drum rotation during the deployment or retraction of unfurlable structures. Also, space structure deployment often involves relative rotations over large, often obtuse angles. The deployment of these structures could be designed along novel lines if such rotations could be directly powered without the weight and power consumption penalties of conventional electric engines.
The rotary paraffin engine concept described by the present invention has been developed to, first, overcome the stroke limitations of paraffin actuators without a decrease of output power. Second, the present invention offers an alternative to existing rotary actuation technology by directly powering rotary, rather than linear, motion. Therefore, it permits the reactivation of the advantages listed above for actuation.